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14.6. Editing a Guest Virtual Machine's configuration file

Instead of using the dumpxml option (refer to Section 14.5.23, “Creating a Virtual Machine XML Dump (Configuration File)”), guest virtual machines can be edited either while they are running or while they are offline. The virsh edit command provides this functionality. For example, to edit the guest virtual machine named rhel6:
Copy to Clipboard Toggle word wrap 
# virsh edit rhel6
This opens a text editor. The default text editor is the $EDITOR shell parameter (set to vi by default).

14.6.1. Adding Multifunction PCI Devices to KVM Guest Virtual Machines

This section will demonstrate how to add multi-function PCI devices to KVM guest virtual machines.
  1. Run the virsh edit [guestname] command to edit the XML configuration file for the guest virtual machine.
  2. In the address type tag, add a multifunction='on' entry for function='0x0'.
    This enables the guest virtual machine to use the multifunction PCI devices.
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    <disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source file='/var/lib/libvirt/images/rhel62-1.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/
</disk>
    For a PCI device with two functions, amend the XML configuration file to include a second device with the same slot number as the first device and a different function number, such as function='0x1'.
    For Example:
    Copy to Clipboard Toggle word wrap 
    <disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source file='/var/lib/libvirt/images/rhel62-1.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source file='/var/lib/libvirt/images/rhel62-2.img'/>
<target dev='vdb' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/>
</disk>
  3. lspci output from the KVM guest virtual machine shows:
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    $ lspci

00:05.0 SCSI storage controller: Red Hat, Inc Virtio block device
00:05.1 SCSI storage controller: Red Hat, Inc Virtio block device
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